1. Field of the Invention
The present invention relates to a refrigeration system of a closed cycle, including: a circulation channel through which a refrigerant circulates; and a dry evaporator incorporated in the circulation channel so as to contact a target heating object.
2. Description of the Prior Art
A refrigeration system of a closed cycle is well known to include a so-called dry evaporator. The refrigeration system is often employed in an interior air conditioner, for example. The evaporation of a refrigerant can be promoted within the dry evaporator under a low pressure, so that atmosphere around the dry evaporator can be cooled down. The refrigerant completely evaporates within the dry evaporator in such an interior air conditioner. The quality of the refrigerant is forced to reach 1.0 within the dry evaporator. Only the refrigerant of gas state is intended to be discharged from the dry evaporator.
A cooling system is in general incorporated in a large-sized computer such as a supercomputer and a main frame. The cooling system is designed to cool a semiconductor device module such as a multichip module (MCM). Acceleration of operating clocks and a higher density of electronic elements are predicted to induce the increased quantity of heat in the semiconductor device module. A higher performance of cooling is expected in the cooling system. It is believed that it becomes difficult for a conventional refrigeration system to reliably restrain an increase in the temperature of the semiconductor device module.
The performance of cooling in the dry evaporator may be considered based on the quantity of heat transfer per unit area, namely, a heat transfer coefficient. A higher heat transfer coefficient serves to reliably prevent the semiconductor device module from an excessive increase in the temperature, even when the semiconductor device module suffers from an extreme generation of heat. Heretofore, no specific proposal has been made to increase the quantity of heat transfer per unit area in the technical field of a refrigeration system of a closed cycle.
It is accordingly an object of the present invention to provide a refrigeration system capable of achieving a higher performance of cooling as compared with a prior art refrigeration system.
According to a first aspect of the present invention, there is provided a refrigeration system comprising: a circulation channel through which a refrigerant circulates; and a dry evaporator incorporated in the circulation channel and designed to keep a quality smaller than 1.0 in evaporating the refrigerant.
In general, the quantity of heat transfer per unit area, namely, a heat transfer coefficient depends on the quality. The heat transfer coefficient remarkably drops when the quality of the refrigerant exceeds a predetermined threshold level before the quality actually reaches 1.0. If the quality of the refrigerant is kept below the predetermined threshold level during vaporization of the refrigerant in the dry evaporator, the dry evaporator is allowed to reliably establish a higher performance of cooling. On the other hand, if a refrigerant completely evaporates in a dry evaporator in a conventional manner, the heat transfer coefficient of the refrigerant remarkably drops after the quality of the refrigerant exceeds the predetermined threshold level. Accordingly, the conventional dry evaporator is forced to absorb heat at a lower heat transfer coefficient, as compared with the dry evaporator of the first aspect. It should be noted that the threshold quality of a refrigerant employed can be set, at a level below 1.0, in an appropriate manner based on the kind of a refrigerant and the capability of cooling required in the dry evaporator.
According to a second aspect of the present invention, there is provided a refrigeration system comprising: a circulation channel through which a refrigerant circulates; a dry evaporator incorporated in the circulation channel and contacting a target heating object; and a subsidiary evaporator incorporated in the circulation channel downstream of the dry evaporator.
It is not necessary to completely evaporate the refrigerant in the dry evaporator of this type of the refrigeration system. The subsidiary evaporator may be employed to accomplish the complete vaporization of the refrigerant, so that the quality of 1.0 is established in the refrigerant discharged out of the subsidiary evaporator. If such a dry refrigerant is supplied to a compressor downstream of the subsidiary evaporator, the compressor can reliably be prevented from a compression of a liquid, which is harmful to the compressor. The dry evaporator contacting a target heating object is allowed to discharge the refrigerant of gas-liquid mixture state. Specifically, the quality of the refrigerant can be kept below a predetermined threshold level during vaporization of the refrigerant in the dry evaporator in the aforementioned manner, so that the dry evaporator is allowed to reliably establish a higher performance of cooling.
According to a third aspect of the present invention, there is provided a method of refrigeration comprising vaporizing a refrigerant within a dry evaporator incorporated in a circulation channel, through which the refrigerant circulates, so as to allow the refrigerant of gas-liquid mixture state to flow out of the dry evaporator.
The method of refrigeration allows the dry evaporator to discharge the refrigerant after incomplete vaporization of the refrigerant in the dry evaporator. The quality of the refrigerant can be kept below a predetermined threshold level during vaporization of the refrigerant in the dry evaporator in the aforementioned manner, so that the dry evaporator is allowed to reliably establish a higher performance of cooling.
The method of refrigeration may further comprise heating the refrigerant flowing out of the dry evaporator so as to completely evaporate the refrigerant of liquid state. If the refrigerant can completely be evaporated before it is introduced into a compressor incorporated in the circulation channel downstream of the dry evaporator, the compressor can reliably be prevented from a compression of a liquid. The compression of a liquid is harmful to the compressor, as conventionally known.
According to a fourth aspect of the present invention, there is provided a refrigeration system comprising: a circulation channel through which a refrigerant circulates; a dry evaporator incorporated in the circulation channel so as to contact a target heating object; a refrigerant outlet defined in the dry evaporator and designed to discharge the refrigerant of gas-liquid mixture state; and a gas-liquid separation filter incorporated in the refrigerant outlet.
Even when the refrigerant is incompletely evaporated in the dry evaporator in this refrigeration system, the gas-liquid separation filter serves to reliably establish the quality of 1.0 for the refrigerant discharged from the dry evaporator. If such a dry refrigerant is introduced into a compressor incorporated in the circulation channel downstream of the dry evaporator, the compressor can reliably be prevented from a compression of a liquid, which is harmful to the compressor. The dry evaporator contacting a target heating object is allowed to discharge the refrigerant of gas-liquid mixture state. Specifically, the quality of the refrigerant can be kept below a predetermined threshold level during vaporization of the refrigerant in the dry evaporator in the aforementioned manner, so that the dry evaporator is allowed to reliably establish a higher performance of cooling.
The respective aforementioned refrigeration systems may include a dry evaporator, comprising: a casing defining a closed space; a refrigerant inlet defined in the casing so as to open at a wall surface; a refrigerant outlet defined in the casing so as to open at a wall surface; and a group of fins inwardly protruding from an inner surface of the casing so as to define a plurality of refrigerant passages extending in parallel from the refrigerant inlet toward the refrigerant outlet, for example. The group of fins serves to enlarge a heat transfer area or contact area between the casing and the refrigerant in the dry evaporator of this type. Heat can reliably be transferred from the casing to the refrigerant in an efficient manner.
In this case, the refrigerant passage preferably gets shorter at a position remoter from a straight line extending from the refrigerant inlet to the refrigerant outlet. In general, the refrigerant discharged out of the refrigerant inlet is supposed to flow along the straight line toward the refrigerant outlet, because the maximum pressure can be maintained along the shortest path. The remoter from the straight line the refrigerant passage is located at, the less pressurized force can be applied to the refrigerant passing through the refrigerant passage, as conventionally known. If the refrigerant passage gets shorter, the refrigerant passage may be released from a larger loss of the applied pressure. The shorter refrigerant passage at a position remoter from the straight line in the aforementioned manner is supposed to equally distribute the refrigerant to the respective refrigerant passage defined between the adjacent fins. The vaporization of the refrigerant can uniformly be achieved within the closed space.
In place of the aforementioned shorter refrigerant passage at a location remoter from the straight line, a refrigerant passage may get wider at a position remoter from the straight line. The wider refrigerant passage is supposed to reduce a larger loss of the applied pressure, so that the refrigerant is equally distributed to the respective refrigerant passage defined between the adjacent fins in the aforementioned manner. The vaporization of the refrigerant can uniformly be achieved within the closed space.
Alternatively, a dry evaporator may include: a casing defining a closed space between a top plate and a bottom plate and contacting a target heating object at the bottom plate; an intermediate plate disposed between the top and bottom plates within the closed space; a vaporization chamber defined between the intermediate and bottom plates; a refrigerant inlet defined in the top plate; an introduction chamber defined between the top and intermediate plates and extending from the refrigerant inlet toward the vaporization chamber; and a discharge chamber defined between the top and intermediate plates and extending from the vaporization chamber toward the refrigerant outlet.
In general, the refrigerant flowing out of the refrigerant outlet can be maintained at a temperature lower than that of the refrigerant flowing through the refrigerant inlet in the dry evaporator, since the negative pressure can be applied to the refrigerant outlet because of the operation of a compressor. The intermediate plate serves to establish a heat exchange between the refrigerants in the refrigerant inlet and outlet based on the difference in temperature. It is possible to restrain variation in the quality of the refrigerant headed toward the vaporization chamber from the refrigerant inlet. A still higher performance of cooling can be achieved in the dry evaporator.
In the above-described dry evaporator, a space between the top and intermediate plates may be set smaller than a space between the bottom and intermediate plates. The smaller space between the top and intermediate plates is expected to accelerate the loss of pressure for the refrigerant in the refrigerant introduction chamber, so that the refrigerant of the liquid state can be prevented from vaporization to the utmost before it is introduced into the vaporization chamber. A still higher performance of cooling can be achieved in the dry evaporator.
In the case where the space is reduced between the top and intermediate plates, it is preferable that the dry evaporator further comprises: an introduction opening defined by an edge of the intermediate plate and designed to connect the introduction and vaporization chambers to each other; and a dike extending along the edge of the intermediate plate so as to swell from the intermediate plate at its surface receiving a refrigerant within the introduction chamber. The dike serves to reliably accelerate the loss of pressure for the refrigerant in the introduction chamber. Moreover, the dike is also expected to establish a uniform flow of the refrigerant over the edge of the intermediate plate, namely, a uniform inflow of the refrigerant into the introduction opening.
The introduction chamber may be designed to by degree expand as it gets closer to the vaporization chamber. The introduction chamber of this type is expected to reliably establish a uniform inflow of the refrigerant into the vaporization chamber. The refrigerant uniformly spreads over the entire vaporization chamber. Additionally, the discharge chamber may be designed to by degree narrow as it gets closer to the refrigerant outlet. The discharge chamber of this type is expected to contribute to establishment of a uniform inflow of the refrigerant into the vaporization chamber.
A plurality of refrigerant passages may be defined within the introduction chamber so as to respectively extend from the refrigerant inlet toward the vaporization chamber. The refrigerant passages serve to uniformly distribute the refrigerant before it is introduced into the vaporization chamber.
An expanded passage is preferably connected to a downstream end of the refrigerant passage. The expanded passage serves to remarkably accelerate the loss of pressure for the refrigerant, so that the vaporization of the refrigerant flowing into the vaporization chamber can be promoted. A performance of cooling can still be improved in the dry evaporator.
Furthermore, the dry evaporator may comprise: a casing defining a closed space between a top plate and a bottom plate and contacting a target heating object at the bottom plate; an intermediate plate disposed between the top and bottom plates within the closed space and connected to an inner surface of the casing; a vaporization chamber defined between the intermediate and bottom plates; a discharge chamber defined between the top and intermediate plates; an inlet duct defining a refrigerant introduction passage penetrating through the discharge chamber so as to reach the vaporization chamber; and an outlet duct surrounding the inlet duct so as to define a refrigerant discharge passage extending from the discharge chamber. The dry evaporator serves to establish a heat exchange between the refrigerant flowing through the refrigerant introduction passage and the refrigerant flowing through the refrigerant discharge passage based on the heat transfer through the wall of the inlet duct. It is thus possible to restrain variation in the quality of the refrigerant headed toward the vaporization chamber from the refrigerant introduction passage to the utmost.
Alternatively, the refrigeration system may for example comprise: a circulation channel through which a refrigerant circulates; a dry evaporator incorporated in the circulation channel and contacting a target heating object at its bottom plate; a vaporization chamber defined within the dry evaporator for inducing a flow of the refrigerant along the bottom plate in a horizontal direction; and a flow controller incorporated in the circulation channel for discharging the refrigerant at a flow enough to establish a gas-liquid separation within the vaporization chamber. When the flow rate or current of the refrigerant introduced into the vaporization chamber is adjusted in this manner, the refrigerant of liquid state, namely, the refrigerant liquid is allowed to flow along the upper surface of the bottom plate within the vaporization chamber under the influence of the gravity. Accordingly, the refrigerant liquid is allowed to uniformly spread over the entire upper surface of the heat transfer or bottom plate. A higher performance of cooling can thus be achieved uniformly over the broader area of the bottom plate.
Furthermore, when the gas-liquid separation is intended within the vaporization chamber, the dry evaporator may comprise: a casing contacting a target heating object at a vertical heat transfer plate; a vaporization chamber defined adjacent the heat transfer plate within the casing; a refrigerant inlet opened at an inner surface of the vaporization chamber; a refrigerant outlet opened at the inner surface of the vaporization chamber at a location above the refrigerant inlet; and a plurality of fins integrally formed on the heat transfer plate within the vaporization chamber so as to define a plurality of refrigerant passages respectively extending in a vertical direction from the refrigerant inlet toward the refrigerant outlet.
A refrigerant discharged from the refrigerant inlet is allowed to flow upward within the vaporization chamber along the heat transfer plate and to finally reach the refrigerant outlet. If the gas-liquid separation is realized in the vaporization chamber, the refrigerant liquid falls on the bottom of the vaporization chamber under the influence of the gravity. The refrigerant liquid received on the bottom plate can uniformly be distributed into the respective refrigerant passages defined between the adjacent fins in the dry evaporator. When the dry evaporator of this type is employed in the refrigeration system of a closed cycle, a flow controller may be incorporated in the circulation channel for discharging the refrigerant at a flow enough to establish the gas-liquid separation within the vaporization chamber.
The dry evaporator of this type may further comprise: a bypass opening formed in the casing so as to open at a lowest position in the vaporization chamber; a duct connected to the casing so as to define a discharge channel extending from the refrigerant outlet; and a bypass channel connecting the bypass opening and the discharge channel to each other. For example, a lubricating agent such as oil may involuntarily be introduced into the vaporization chamber in the dry evaporator employed in the refrigeration system. The oil stored in the vaporization chamber can be led to the discharge channel or the circulation channel through the bypass channel under the influence of the difference in pressure between the refrigerant inlet and outlet. It is possible to prevent the oil, discharged from the compressor, from staying within the vaporization chamber.
Furthermore, when the gas-liquid separation is intended in the vaporization chamber, a dry evaporator still may comprise: a casing defining a vaporization chamber between a vertical heat transfer plate and a vertical back plate and contacting a target heating object at the heat transfer plate; a partition plate disposed between the heat transfer plate and the back plate so as to divide an upper portion of the vaporization chamber into an introduction space adjacent the heat transfer plate and a discharge space adjacent the back plate; a refrigerant inlet opened at the inner surface of the introduction space; and a refrigerant outlet opened at the inner surface of the discharge space. In this case, the depth of the lower portion of the vaporization chamber is set larger than the space or distance measured between the heat transfer plate and the partition plate. Here, the depth should be measured from the lower edge of the partition plate in the vertical direction. The dry evaporator of this type enables a jagged increase in the sectional area of the vaporization chamber when the refrigerant flows around the lower edge of the partition plate. The remarkable enlargement of the sectional area promotes the gas-liquid separation of the refrigerant in the vaporization chamber. Here, the sectional area of the vaporization chamber is measured based on a profile in a plane perpendicular to the direction of the flow or current of the refrigerant. When the dry evaporator of this type is employed in the refrigeration system of a closed cycle, a flow controller may be incorporated in the circulation channel for discharging the refrigerant at a flow enough to establish the gas-liquid separation within the vaporization chamber.
Otherwise, the dry evaporator may comprise a casing contacting a target heating object at a vertical heat transfer plate; and a micro channel formed on the heat transfer plate within the casing so as to extend in a vertical direction, said micro channel having a width enough to realize a capillary action of a refrigerant.
The dry evaporator of this kind allows the refrigerant liquid to ascend along the micro channel with the assistance of the capillary action overcoming the gravity. Accordingly, the heat transfer plate is allowed to hold the refrigerant liquid over a broader area irrespective of the level of the refrigerant liquid at the bottom of the casing. The refrigerant liquid is forced to vaporize in an efficient manner by heat transmitted to the heat transfer plate. The vaporization of the refrigerant liquid can thus be accelerated. When the dry evaporator of this type is employed in a refrigeration system of a closed cycle, a flow controller may be incorporated in the circulation channel for discharging the refrigerant at a flow enough to establish the gas-liquid separation within the vaporization chamber.
Furthermore, a dry evaporator may include: a casing contacting a target heating object at a heat transfer plate; a first wall surface defined on the heat transfer plate within the casing so as to extend from a datum line; and a second wall surface connected to the first wall surface at the datum line and opposed to the first wall surface. The space between the first and second wall surfaces gets larger as the second wall surface is distanced apart from the datum line. A micro channel is defined between the first and second wall surfaces so as to establish a capillary action of a refrigerant.
The dry evaporator enables generation of a larger surface tension at the surface of the refrigerant liquid facing the datum line when the refrigerant liquid is introduced between the first and second wall surfaces. The refrigerant liquid is sucked toward the datum line between the first and second wall surfaces with the assistance of the surface tension. A larger quantity of the refrigerant liquid can thus be held between the first and second wall surfaces. The vaporization of the refrigerant liquid can be accelerated.
An expanded groove may be defined at least on any of the first and second wall surfaces so as to extend along the datum line within the micro channel. The expanded groove serves to reliably hold a still larger quantity of the refrigerant liquid introduced between the first and second wall surfaces. The vaporization of the refrigerant liquid can still further be accelerated.
A dry evaporator may include: a casing contacting a target heating object at a heat transfer plate; a first erosion surface defined on the heat transfer plate within the casing; and a second erosion surface opposed to the first erosion surface so as to define a micro channel between the first and second erosion surfaces. A fine asperity can be established on the first and second erosion surfaces. Such a fine asperity serves to achieve an enlarged heat transfer area over the heat transfer plate and an improved wetness to the refrigerant liquid. The vaporization of the refrigerant liquid can still further be accelerated.
Alternatively, a dry evaporator may include: a casing contacting a target heating object at a heat transfer plate; a first wall surface defined on the heat transfer plate within the casing; a second wall surface opposed to the first wall surface so as to define a micro channel between the first and second wall surfaces; and heat conductive fine particles adhered to the first and second wall surfaces, respectively. The heat conductive fine particles serve to achieve an enlarged heat transfer area over the heat transfer plate and an improved wetness to the refrigerant liquid. The vaporization of the refrigerant liquid can thus be accelerated.
Furthermore, a refrigeration system may comprise: a circulation channel through which a refrigerant circulates; a compressor incorporated in the circulation channel and designed to discharge the refrigerant of gas state at a high pressure; a dry evaporator incorporated in the circulation channel so as to contact a target heating object at a heat transfer plate; a jet nozzle inserting a tip end into an interior of the dry evaporator; and a bypass channel diverging from the circulation channel downstream of the compressor so as to supply the refrigerant of gas state toward the jet nozzle.
During the operation of the compressor, the refrigerant of gas state, namely, the refrigerant gas, discharged from the compressor at a high pressure, is supplied to the jet nozzle through the bypass channel. The supplied refrigerant gas can be discharged out of the jet nozzle toward the refrigerant of liquid state at the bottom of the dry evaporator, for example. Drops of the refrigerant liquid may splash upward from the surface of the refrigerant liquid at the bottom of the dry evaporator. If the splashed refrigerant liquid is allowed to stick to the heat transfer plate, the refrigerant liquid can be held on the heat transfer plate over a broader area. The vaporization of the refrigerant liquid can be promoted in the dry evaporator. Simultaneously, the discharged refrigerant gas may also lead to stir of the refrigerant liquid at the bottom of the dry evaporator. The stir of the refrigerant liquid may contribute to a uniform distribution of the refrigerant liquid within the dry evaporator.
A flow controller, such as an electronic controlled valve, may be incorporated in the bypass channel. If the flow controller is allowed to control the flow or current of the refrigerant gas passing through the bypass channel, the jet amount of the refrigerant gas introduced into the dry evaporator at a high pressure can properly be adjusted. The vapor pressure within the dry evaporator. If the vapor pressure can properly be controlled in this manner, the boiling point of the refrigerant can properly be adjusted in the dry evaporator.
The aforementioned refrigeration system may be employed to cool a semiconductor device module such as a multichip module (MCM) in a large-sized computer such as a supercomputer, a main frame, and the like. In employment of the refrigeration system, a semiconductor device module may be prepared to include: a printed circuit board; a semiconductor element mounted on the printed circuit board; a dry evaporator contacting the semiconductor element and applicable to a refrigeration system of a closed cycle; and a heat insulator member containing the dry evaporator so as to fix the dry evaporator to the printed circuit board.
If the dry evaporator can be fixed to the printed circuit board in this manner, the semiconductor device module and the dry evaporator can be handled as a unit. The operability can be improved in replacement or maintenance of the semiconductor device module. The heat insulator member serves to prevent condensation and/or frost over the surface of the dry evaporator.
The heat insulator member may be divided into a first half piece containing the printed circuit board, and a second half piece containing the dry evaporator and detachably coupled to the first half piece. Detachment of the second half piece from the first half piece enables exposure of the surface of the printed circuit board. The semiconductor element or chip can be maintained or replaced on the printed circuit board without disturbance from the heat insulator member. The operability in replacement and/or maintenance of the semiconductor device module can further be improved.
A heater may be incorporated in the heat insulator member in the aforementioned semiconductor device module. The heater is designed to heat the heat insulator member. Incorporation of the heater in this manner thus enables reduction in the thickness or volume of the heat insulator member, when the prevention of condensation and/or frost is intended on the surface of the dry evaporator. The semiconductor device module can be made compact. The compact semiconductor device module may contribute to a higher density in arrangement of the semiconductor device module.
A heat conductive member may be interposed between the heater and the dry evaporator. The heat conductive member is preferably designed to have a property allowing heat to conduct at a first specific thermal conductivity in a vertical direction oriented from the heater to the dry evaporator and to conduct at a second specific thermal conductivity larger than the first specific thermal conductivity in a plane perpendicular to the vertical direction. When heat from the heater is transferred to the heat conductive member of the type, the heat conductive member serves to spread the heat from the heater over a broader area along the plane perpendicular to the vertical direction within the heat insulator member. Irrespective of the size of the heater, the heat insulator member can be heated over the broader area. On the other hand, the heat from the heater hardly reaches the dry evaporator, so that the performance of cooling in the dry evaporator is prevented from unnecessarily being consumed.
In addition, a semiconductor device module may comprise: a printed circuit board; a semiconductor element mounted on the upper side of the printed circuit board; a dry evaporator contacting the semiconductor element and applicable to a refrigeration system of a closed cycle; an input/output pin standing on the lower side of the printed circuit board; and a heater attached to the lower side of the printed circuit board.
In general, the input/output pin is made from a metallic material. The metallic input/output pin is easily cooled down under the influence of performance of cooling by the dry evaporator. If the input/output pin is excessively cooled down, the surface of the input/output pin tends to suffer from condensation and/or frost. Attachment of the heater to the lower side of the printed circuit board enables transmission of heat to the input/output pin, so that the input/output pin can be prevented from generation of condensation and/or frost on its surface.
Furthermore, a semiconductor device module may comprise: a printed circuit board; a semiconductor element mounted on the upper side of the printed circuit board; a dry evaporator contacting the semiconductor element and applicable to a refrigeration system of a closed cycle; an input/output pin standing on the lower side of the printed circuit board; and a heat insulator member containing the input/output pin. The heat insulator member contributes to prevention of condensation and/or frost on the surface of the input/output pin.
Furthermore, a semiconductor device module may comprise: a printed circuit board; a semiconductor element mounted on the printed circuit board; a heat transfer plate contacting the semiconductor element; a dry evaporator contacting the heat transfer plate and applicable to a refrigeration system of a closed cycle; a bolt for fixation received in a through bore defined in the heat transfer plate; and a low heat conductive member interposed between the heat transfer plate and the bolt. With this arrangement, when the dry evaporator is attached to the printed circuit board, it is possible to restrain a heat transfer between the dry evaporator and the printed circuit board. Accordingly, the printed circuit board can be prevented from an excessive cooling under the influence of the dry evaporator.
Furthermore, a semiconductor device module may comprise: a printed circuit board; a semiconductor element mounted on the printed circuit board; a dry evaporator contacting the semiconductor element and applicable to a refrigeration system of a closed cycle; and a heater contacting the dry evaporator.
In general, when the semiconductor device module is to be replaced or maintained, the semiconductor device module should return to the room temperature. If the semiconductor device module is exposed to the normal atmosphere before it has returned to the room temperature, condensation and/or frost may be induced on the surface of the semiconductor device module. Even when the semiconductor device module has been cooled down under the influence of the refrigeration system, the semiconductor device module can rapidly be heated by receiving heat from the heater. Since the rise in temperature can be accelerated by the heater as compared with the natural radiation of heat, the working time of replacement or maintenance can remarkably be shortened. The heater may be attached to the heat transfer plate disposed between the dry evaporator and the printed circuit board.
When the heater of the aforementioned type is employed, a thermal sensor is preferably mounted on the printed circuit board. The thermal sensor can be utilized to prevent an excessive rise in temperature by the heater, for example. Based on the temperature detected by the thermal sensor, the operation of the heater can reliably be terminated before the printed circuit board actually suffers from an excessive rise in temperature.
In general, any of the aforementioned semiconductor device modules may be received on a large-sized printed circuit board. A connector may be mounted on the large-sized printed circuit board so as to hold the semiconductor device module on the large-sized printed circuit board. When the prevention of condensation and/or frost on the surface of the input/output pin is intended in the aforementioned manner, such a connector for a semiconductor device module may comprise: an electric conductive member receiving an input/output pin protruding from the semiconductor device module; and a heater disposed to surround the electric conductive member.
When the aforementioned refrigeration system is intentionally employed to cool the semiconductor device module, a semiconductor device enclosure unit may be prepared to include a box-shaped enclosure designed to contain a dry evaporator contacting a semiconductor element on a printed circuit board; and a dehumidifier designed to release moisture from a closed space defined in the box-shaped enclosure to an open space outside the box-shaped enclosure.
When the dehumidifier serves to release moisture toward the open space outside the semiconductor device enclosure unit, a dry atmosphere can be established within the box-shaped enclosure. The dry atmosphere serves to lower the dew point of the vapor included in the air. Accordingly, condensation and/or frost can reliably be prevented on the surfaces of the printed circuit board, the semiconductor element and the dry evaporator within the box-shaped enclosure.
In this case, a heater may be attached to the inner surface of the box-shaped enclosure. The heater may be utilized when the semiconductor element is to be replaced or maintained. The heat from the heater serves to heat the atmosphere within the box-shaped enclosure. When the atmosphere in the box-shaped enclosure is heated, a rise in temperature can be established on the inner surface of the box-shaped enclosure and the surface of the printed circuit board. If the inner surface of the box-shaped enclosure and the surface of the printed circuit board are exposed to an exterior atmosphere of a room temperature after the atmosphere has been heated within the box-shaped enclosure in the aforementioned manner, it is possible to prevent condensation on the inner surface of the box-shaped enclosure and the surface of the printed circuit board. Since the rise in temperature can be accelerated as compared with the natural radiation of heat, the working time of replacement or maintenance can remarkably be shortened.
Otherwise, a semiconductor device enclosure unit may comprise: a first box-shaped enclosure designed to contain a dry evaporator contacting a semiconductor element on a printed circuit board; a second box-shaped enclosure designed to contain the first box-shaped enclosure; a first dehumidifier designed to release moisture from a closed space defined in the first box-shaped enclosure to an outside; and a second dehumidifier designed to release moisture from a closed space within the second box-shaped enclosure to an open space outside the second box-shaped enclosure. The semiconductor device enclosure unit of this type serves to further efficiently release moisture in the vicinity of the printed circuit board outward to the open space. Even when the atmosphere in the first box-shaped enclosure reaches a cryogenic temperature, it is still possible to reliably prevent condensation and/or frost within the first box-shaped enclosure. In this case, the aforementioned heater may be attached at least to the inner surface of the first box-shaped enclosure.
Furthermore, a semiconductor device module may comprise: a printed circuit board; a semiconductor element mounted on the printed circuit board; a casing attached to the printed circuit board and designed to define a refrigerant passage; and a cooling element extending across the refrigerant passage and designed to protrude its tip end out of the casing. The tip end is allowed to contact the semiconductor element. In this semiconductor device module, the cooling element serves to transfer heat, generated at the semiconductor element, to the refrigerant in an efficient manner.